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Q62182: C4058 Error with /qc Compile Option

Article: Q62182
Product(s): See article
Version(s): 6.00   | 6.00
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | buglist6.00 | mspl13_c
Last Modified: 17-JUL-1990

The C4058 warning message can be generated in error if the /qc switch
(quick compile) is used. If the warning disappears after the /qc
switch is removed, the warning can be ignored.

Sample Code
-----------

 1. #include <math.h>
 2.
 3. void main (void) ;
 4.
 5. void main (void)
 6. {
 7.    double a ;
 8.
 9.    a = cos (3.2) ;
10.    a = sin (2.2) ;
11.    a = atan (5.0) ;
12. }

Compile with the following options:

   cl /c /qc /W4 /Alfw fpburgr.c

The following warning is given on the three assignment statements that
reference "a":

   Warning C4058: address of automatic (local) variable taken, DS != SS

The /Alfw switch (used in multithreaded programs, dynamic link
libraries, and Windows programming), instructs the compiler to assume
DS != SS with DS fixed. Typically, this warning will come about when a
program de-references a near pointer that is automatic (local). In this
case, the warning is invalid.

The following are two different ways of working around the problem:

1. Compile with /Alfu. This assumes that DS != SS, and causes DS to be
   reloaded upon function entry.

2. Turn off the /qc compile option.

Microsoft has confirmed this to be a problem with C version 6.00. We
are researching this problem and will post new information here as it
becomes available.

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